Friends said Abdukadir Mohamed Abdukadir, who was linked to alleged terror plots in Kenya, came to Britain in 2007 and spent time in London before going to Somalia the next year, the BBC said Friday.
A U.S. Navy SEAL operation to capture him Oct. 5 failed.
The raid followed an attack on the Westgate shopping mall in Nairobi, Kenya, Sept. 21 that lasted four days and in which at least 67 people died.
Al-Shabaab, based in Somalia, claimed responsibility for the siege, but the BBC said it wasn't clear what, if any, role Abdukadir played in the attack.
Also known as Ikrima, Abdukadir is believed to be a recruiter of foreign fighters, and a key link between al-Shabaab and al-Qaida in the Arabian Peninsula, based in Yemen, the BBC said.
In 2004, Abdukadir traveled to Norway, where he unsuccessfully sought asylum.
Meanwhile, U.N. Secretary General Ban Ki-moon said 4,500 more troops are needed by the U.N.-backed African Union force fighting al-Shabaab in Somalia, the BBC said.
In a report to the U.N. Security Council, Ban said military advances against al-Shabaab could be reversed and expressed concern that an attack similar to that on the Nairobi mall could be repeated if the 18,000-member force was not increased.